Same issue here on 2021 M3P from Freemont...usually happens right after I accelerate hard then stop for a traffic light or something...its definitely coming from the front and almost definitely the heat pump activating. Gave my car in for servicing this morning for some delivery day issues and I cited that noise/vibration as a problem, but I'm not holding my breath for any sort of fix there. They'll probably just chalk it up to standard heat pump operation. I hopeee they put some insulation around it. Will let you know tomorrow when I pick it up.
Interesting. When I accelerate hard and then slow down, I hear a (pretty loud) fan sound but for me, it's a smooth fan sound: just a wooshing of air. No vibration. Seemed normal to me: probably cooling things down after a "hit".
Mike